The present invention relates generally to a well apparatus for use in controlling the flow of fluids within the well. In particular, the present invention relates to means for stopping the uncontrolled flow of fluids from a well blowout during drilling or production of oil and gas.
In the drilling or production of oil and gas, accidents such as equipment malfunctions or the like occasionaly result in a condition known as a blowout. In such instances, the fluids under substantial underground pressure flow uncontrollably to the surface, i.e. a sea floor or a land surface. Often when such uncontrolled well flow occurs, the combustible fluids leaving the wellhead are ignited, causing a fire.
Well blowouts should be capped as quickly as possible in order to prevent a further loss of the valuable resource, as well as to prevent pollution of the environment. However, to control the flow from a burning or damaged well, it is necessary to close the wellbore at a location where the casing and tubing are stillundamaged and accessible.
In one commonly used method, additional wellbores are drilled to intersect the uncontrolled wellbore so that a plugging fluid such as cement, a heavy drilling mud or the like can be pumped into the formation to kill the well. Another method uses explosives to blow out the fire and subsequently seal off the well at the surface wellhead. These procedures, however, are hazardous, costly and time consuming and also permit the well effluents to flow onto and pollute the surrounding area. Even after the combustion is stopped, the capping operation remains extremely dangerous in that the highly combustible effluents may ignite at any time. Moreover, in offshore operation, heavy wave action may severely limit the operation and can also appreciably increase the danger of the operation.
Another method for extinguishing the uncontrolled flow of fluids is described in U.S. Pat. No. 2,000,381. This technique includes the construction of an underground cage in which flow control devices are located and controlled via a tunnel leading from the surface to the cage. The technique also includes the application of a piercing means whereby the well casing and production tubing string may be pierced so that fire-quenching steam or other fluid or gas can be supplied to extinguish the burning well. Another underground method of closing the well is disclosed in U.S. Pat. No. 3,277,964, wherein two or three tunnels are directed to the location adjacent to the undamaged wellhead. The technique also includes a tapping process which is carried out at the lower part of the production tubing, followed by forming a crimp in the upper production tubing. The forming process may use a pair of hydraulic rams. Thereafter, the discharge is bled and plugging material is injected into the well. To complete the operation, both of the aforesaid techniques often require personnel to go down along the tunnel to install the equipment on the wellhead. Both operations are therefore considered to be dangerous, especially in underwater wells in offshore operations. Furthermore, the operations are very costly and time consuming.
In offshore operations, various techniques are known for the purpose of closing off the underwater well against the uncontrolled discharge of gas or oil from the well. For example, U.S. Pat. No. 3,631,928 shows an apparatus and method for drilling into the well casing and closing the well by pumping mud or cement into the well. The drilling process is usually done by sending a diver down to the wellhead at the ocean floor. Similarly, in U.S. Pat. No. 3,647,000 divers are sent to the location below the water surface at the wellhead in order to restrict the effluence flow by crimping the casing walls and introducing materials which form a plug beneath the restriction and stop the effluent flow. The method shown in U.S. Pat. No. 4,163,477 includes a shut-off device which is activated by a gas generator. The gas generator is brought down by a diver to the ocean floor and remote control of the activation point is provided. These methods, however, are costly and time consuming. Moreover, sending a diver down below the water surface is dangerous since debris from above may fall on him. Further, fallen debris may impede the diver's access to the wellhead or the control console and may cause him to mishandle the equipment. Heavy wave action may also severely limit closing operation by the diver and can also appreciably increase the danger of the operation.
U.S. Pat. Nos. 3,405,387 and 3,590,920 use sound waves and radio waves, respectively, to activate underwater well control devices for use in closing off the uncontrolled well. Such devices, however, may be easily triggered by false or inadvertant signals.
There are other examples of shut-off devices in the prior art which are remote controlled utilizing a hydraulic control system. Fluid is pressurized and pumped into the hydraulic control line to close the valves or rams. Examples of such devices are shown in U.S. Pat. Nos. 3,512,554; 3,926,256 and 4,193,574. In hydraulically controlled shut-off devices, however, a certain disadvantage is present in that the hydraulic control line leading to the shut-off device may be damaged, or corroded, or otherwise leak to permit reduction of the hydraulic control pressure, thereby causing the device not to close properly. These problems are frequently found in the hydraulic control line for underwater operation. Another disadvantage of the use of hydraulically controlled shut-off devices is that extremely high hydraulic control pressures are sometimes required. This means that hydraulic control lines at the surface must carry high hydraulic pressure. These high hydraulic control pressures constitute a potential hazard to personnel working on the platform and/or around the control console.
U.K. Pat. No. 2,091,321A discloses a method for use in closing off an uncontrolled blowout of underwater wells. The method is carried out by positioning an apparatus comprising slidable base means, including support means for positioning a pipe engaging means and a pipe straightener means, above the uncontrolled wellbore. The operation includes passing a continuous pipe into the wellbore through the slidable base means to near the bottom of the wellbore. Thereafter, a plugging material is pumped into the wellbore to control and kill the well. Due to construction of the system and operating characteristics, there are some limitations confronting the operator which make it difficult to properly install the slidable base means around the wellhead. Moreover, the apparatus is not suitable for the control of fluid flow from wells which are burning. Further, this method is costly and time consuming.